FBI divers use sonar in hunt for Iowa cousins

Divers search Meyers Lake for missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last week, Friday, July 20, 2012, in Evansdale, Iowa. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)
— AP

Divers search Meyers Lake for missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last week, Friday, July 20, 2012, in Evansdale, Iowa. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)
/ AP

Law enforcement authorities conduct surveillance for an FBI dive team in search of missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, Friday, July 20, 2012, in Evansdale, Iowa, who disappeared last Friday at Meyers Lake. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)— AP

Law enforcement authorities conduct surveillance for an FBI dive team in search of missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, Friday, July 20, 2012, in Evansdale, Iowa, who disappeared last Friday at Meyers Lake. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)
/ AP

Law enforcement authorities conduct surveillance for an FBI dive team in search of missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last Friday at Meyers Lake, Friday, July 20, 2012, in Evansdale, Iowa. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)— AP

Law enforcement authorities conduct surveillance for an FBI dive team in search of missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last Friday at Meyers Lake, Friday, July 20, 2012, in Evansdale, Iowa. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)
/ AP

Law enforcement authorities conduct surveillance for an FBI dive team, Friday, July 20, 2012, in Evansdale, Iowa, in search of missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last Friday at Meyers Lake. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)— AP

Law enforcement authorities conduct surveillance for an FBI dive team, Friday, July 20, 2012, in Evansdale, Iowa, in search of missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last Friday at Meyers Lake. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)
/ AP

Divers search Meyers Lake for missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last week, Friday, July 20, 2012, in Evansdale, Iowa. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)— AP

Divers search Meyers Lake for missing children Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared last week, Friday, July 20, 2012, in Evansdale, Iowa. The girls' bikes were found last Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)
/ AP

This combo made from undated photos provided by Black Hawk County police shows cousins Lyric Cook-Morrissey, 10, left, and Elizabeth Collins, 8, who have been missing since Friday afternoon, July 13, 2012. The girls were last seen Friday afternoon leaving their grandmother's house. (AP Photo/Black Hawk County Police via Waterloo Courier)— AP

This combo made from undated photos provided by Black Hawk County police shows cousins Lyric Cook-Morrissey, 10, left, and Elizabeth Collins, 8, who have been missing since Friday afternoon, July 13, 2012. The girls were last seen Friday afternoon leaving their grandmother's house. (AP Photo/Black Hawk County Police via Waterloo Courier)
/ AP

EVANSDALE, Iowa 
An FBI dive team searched an Iowa lake early Friday for signs of two young girls who disappeared in the area a week ago.

Meyers Lake is about a mile from the Evansdale home where 10-year-old Lyric Cook-Morrissey and her cousin, 8-year-old Elizabeth Collins, were last seen on July 13. The girls set off on a bike ride and never returned. Their bicycles were found on a path near the lake.

The 26-acre body of water near an interstate in northeast Iowa is stocked with fish and popular for fishing. Investigators dredged it after the girls disappeared and then began draining the water. They halted the draining operation Thursday because the FBI team needs at least 6 feet of water for its sonar equipment to function.

On Friday, parts of the lake were nearly empty of water, with the sandy and muddy bottom showing, but other areas still had up to 20 feet of murky water. FBI agents made laps of the lake in an Iowa Department of Natural Resources boat, while four other agents slowly walked along the shore, looking for evidence. They waded into water that ranged from ankle-deep to chest-high.

Black Hawk County Chief Deputy Rick Abben said agents were looking for the girls' bodies as well as anything in the lake that might be evidence. He said a search last weekend with sonar equipment operated by DNR found nothing in the lake, but FBI's technology is far superior. He noted the FBI only has a few dive teams nationwide.

"It's high-tech. It should be pretty good stuff," he said.

The FBI uses two kinds of sonar - one that can detect debris in murky water and another that provides a 360-degree analysis of the bottom of the lake. That device is mounted on a tripod that sends signals to computers on the surface helping direct divers where to search.

After circling the lake for two hours, the agents in the boat pulled a shore, got out and appeared to be discussing the operation. FBI spokeswoman Sandy Breault said 10 dive team members were there, including those in the boat and on shore, but none had yet gone under the surface of the water.

About 20 onlookers, mostly residents who had volunteered with the search, waited in the park near the lake for news of developments.

Angie Webb, 29, a teacher at the elementary school in the Waterloo suburb that Elizabeth attended, said she was holding out hope that the FBI divers would be unsuccessful and that the girls would show up alive.

"If they are in the lake, that's the worst-case scenario. You've got to be hopeful," Webb said.

On Thursday, tension between investigators and Lyric's parents seemed to reach a breaking point, with police suggesting they weren't cooperating and the couple consulting an attorney.

Tammy Brousseau, an aunt of both girls, told The Associated Press that Misty Cook-Morrissey and Dan Morrissey feel they're being treated as suspects.

She said an attorney advised the couple on Wednesday to stop talking to reporters, discontinue television interviews and not agree to take any more polygraph tests, Brousseau said. Cook-Morrissey told KCCI TV in Des Moines that she had undergone such tests during police interviews, and Abben confirmed Thursday that the parents had taken some polygraph tests.